1. Field of the Invention
The present invention relates to generally to electromagnetic relays and, in particular, to a structure for electromagnetic relays having a core, inserted through, a center of a bobbin, to be attached onto a yoke.
2. Description of the Prior Art
A conventional electromagnetic relay has a core attached to a yoke by staking, as disclosed, for example, in Japanese Unexamined Utility Model Publication No. S57-72540. With such stake-fastening, however, the assembling of an armature and a leaf spring, referred to as an armature spring, onto a core had to be performed after the clamp-fastening step of the core and the yoke, due to necessity of working processes. As a result, it has been difficult to obtain accurate control of the angle of attachment of the yoke with the armature.
Another electromagnetic relay structure is disclosed in Japanese Unexamined Utility Model Publication No. H2-104547, wherein a core is press-fitted into a cutout formed in a yoke. In this structure, the core has a smaller diameter portion formed adjacent one end thereof, and a cutout is provided in a bottom plate of an L-shaped yoke, thereby allowing the smaller diameter portion to be press-fitted in the cutout of the yoke.
With this structure, the problem concerning the accuracy control of the attachment angle for the yoke and the armature is solved. However, a large amount of press-fitting force is initially required during press-fitting of the core into the yoke, worsening the operation efficiency. Also, the bottom plate of the yoke is cut away by a peripheral edge of a larger diameter portion of the core, thereby producing chips. This creates a new problem in that the chips are adhered to contact portions or other operating portions within a case of the electromagnetic relay, thereby causing poor operation.